The present invention relates to the field of optical networks, and particularly to constructing an optical node in ultra long haul backbone networks.
Next generation of backbone networks may interconnect optical nodes by using dense wavelength division multiplexer (DWDM), ultra long haul regeneration free transmission, optical cross connect (OXC), or optical add drop multiplexer (OADM) technologies. The drive is less for the sheer capacity boost but more for the fundamental shift in replacing the voice-centric, hard-to-scale, and slow-to-provision digital network with a data-centric, scalable, and easy-to-provision optical network.
An optical node typically performs the following basic functions. The first function is optical 2R (regenerate and reshape), including high-power and low-noise optical amplifications and dispersion management. The second function is DWDM maintenances, including gain equalization and dispersion slope control. The third function is 100% wavelength processing, including 100% wavelength manipulation such as OADM or OXC. OXC must have all optical bypassing to ensure the full transparency of the optical layer. The fourth function is wavelength monitoring, which comprises monitoring of channel wavelength, optical signal-to-noise ratio (OSNR), and all other optical intelligence. Power consumption and channel density are also significant [figure-of-merit] figures-of-merit. A shortcoming in a conventional optical node is the lack of capabilities to deal with high-power and low-noise optical amplifications, dispersion slope control, gain equalization, OADM, and OXC all the same time.
Accordingly, it is desirable to have an optical node that has the functional power, features, and performance for operation in ultra long haul networks.
The invention discloses an optical node for operation in an ultra long haul backbone network that provides DWDM optical transmission and wavelength networking functionalities. The optical node is designed with capabilities for amplification, dispersion compensation, and add/drop functionalities. In one embodiment, three erbium-doped fiber amplifiers (EDFA) are cascaded using low nonlinearity and low loss dispersion compensating module (DCM).
Advantageously, the optical node in the present invention produces a more efficient power consumption and channel density. The present invention also advantageously does not rely on, but is complementary to, other ultra long haul technologies, e.g. Raman amplification, EDFA band splitting, and return-to-zero (RZ) coding.
Other structures and methods are disclosed in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims.